1. Field of the Invention
The present invention relates to an image formation apparatus for a printing machine, such as an inkjet image formation apparatus, configured to eject ink onto and thereby form an image on a print sheet being conveyed along a conveyance path.
2. Description of the Related Art
Heretofore, there have been line-type inkjet recording apparatuses as a type of image formation apparatuses. In such a line-type inkjet recording apparatus, a long recording head (line-type long recording head) is used in which ink ejection nozzles are arranged in an array which is as wide as or wider than the width of a print area. Without moving the recording head, the line-type inkjet recording apparatus forms an image by ejecting ink droplets from nozzles of the ink heads onto a recording medium below the ink heads while moving and conveying the recording medium relative to the recording head in a direction crossing the nozzle arrangement direction.
As shown in FIG. 16A, an airstream W1 (hereinafter called a conveyance airstream) flowing from upstream to downstream in a conveyance direction of a recording medium is generated when the recording medium is conveyed at a position just below the recording head. Accordingly, in a noncontact printing method in which ink droplets 20 are ejected onto a print sheet 10 from a nozzle 121 of an ink head 120, the ink droplets 20 are drifted to a downstream side in the conveyance direction of the print sheet 10 under the influence of the conveyance airstream W1, and attached to the print sheet 10 at positions deviated from their intended trajectory. This is so-called landing deviation, and causes deterioration in image quality.
For example, Patent Document 1 copes with such a problem. In the technique of Patent Document 1, when ink droplets are ejected while a recording medium and an ink head having multiple nozzles are moved relative to each other in a direction crossing a nozzle arrangement direction, the ejection is controlled by increasing the ejection speed for a smaller size of droplets. This suppresses landing deviation of ink droplets attributable to the conveyance airstream.
[Patent Document 1] Japanese Patent Application Publication No. 2010-173178